We just got our 14.35kw solar system installed. No batteries due to cost & our power company has a decent net metering policy. I have been thinking of more cost effective ways of having battery storage & after reading about the Tesla battery packs, thought of using a repurposed EV battery pack. I know I would need a huge inverter also. Just curious if anyone has done this or any useful websites about it.
In reply to mdshaw :
I see a lot of people trying it on University of Tubes videos. But I also think the cost of large storage using LiFePO4 batteries is getting so low, you may be better off getting a large set of those.
The one good thing about former EV batteries is that even depleted, they should have more than enough storage for your home.
But this is where I will also mention- https://diysolarforum.com/
Since you're concerned about cost, you'll need to look at the payback period for installing batteries and inverter to see if it makes economic sense.
In reply to stuart in mn :
Of course cost is a consideration like with anything. I diy a lot of things (everything) around our house. Was just thinking it would be good someday to have batteries. Like today it's over cast & raining.
I like taking discarded items & making something that saves us $$. Not for the green aspect but totally in the $$ saving aspect.
In reply to alfadriver :
I'll be on there for sure, thanks.
IMHO lithium battery storage for a PV system is really not a place to be DIYing things unless you really know what you're doing. Charging and maintaining large lithium metal batteries is not a simple problem and the risk of fire is real.
If I wanted to DIY battery storage I'd look at lead-acid. Sure it's not as sexy but it's a whole lot easier to charge, it's not going to burn my house down, and I really don't care how heavy it is if it's sitting in a box in my yard.
In reply to codrus (Forum Supporter) :
That's why LiFePO4 is popular for DIYers- they don't have the risk for fire.
alfadriver said:In reply to codrus (Forum Supporter) :
That's why LiFePO4 is popular for DIYers- they don't have the risk for fire.
My understanding is that they have a smaller but non-zero risk of fire.
Regardless, "used EV packs" are not usually LiFePO4.
I've been reading about a company that developing a battery that doesn't use any hard to get or expensive materials. A form of iron or iron oxide is used to store power. Not sure how it works but it's supposed to be way cheaper to make. The last report I read was in the WSJ a few weeks back.
In reply to codrus (Forum Supporter) :
I've accidentally tried to start a fire by drilling through the side- it got hot and made a lot of noise, but no fire. With a good battery management system as well as a charge control system, they are pretty safe.
As for used EV packs, true, except for Tesla. Who famously use LiIon batteries.
jimbbski said:I've been reading about a company that developing a battery that doesn't use any hard to get or expensive materials. A form of iron or iron oxide is used to store power. Not sure how it works but it's supposed to be way cheaper to make. The last report I read was in the WSJ a few weeks back.
There are already iron-nickel batteries that have been around for a long time, which are very reusable, too. Great batteries, but heavy has heck. But, yea, I also read there are a number of people trying to use common material batteries- I hope they all have success. Every single one of the- options FTW.
codrus (Forum Supporter) said:If I wanted to DIY battery storage I'd look at lead-acid. Sure it's not as Efficient but it's a whole lot easier to charge, it's not going to burn my house down, and I really don't care how heavy it is if it's sitting in a box in my yard.
Is that what you meant to say? DIY solutions and sexy don't really go that well together that well, so I doubt that was a consideration.
alfadriver said:But this is where I will also mention- https://diysolarforum.com/
That just cost me a TON of reading! But ought to save me a ton of headaches as I learn the modern solar tech. Thanks for the link. Looks like a great site.
In reply to 03Panther :
You are very welcome- there are some very helpful people there. Some, not so much, but mostly good people.
alfadriver said:In reply to 03Panther :
You are very welcome- there are some very helpful people there. Some, not so much, but mostly good people.
So, normal. 
I actually joined an Astro van forum, but posted very little.
Here was 2nd. But first I've done much on. Better, but still...
'Course I've gotten angry enough to show my childish side a few time, myself!
3 Beemer forums now, for the K75s; I've gained some insight on how to participate, from you guys on here!!!!
mdshaw said:We just got our 14.35kw solar system installed. No batteries due to cost & our power company has a decent net metering policy. I have been thinking of more cost effective ways of having battery storage & after reading about the Tesla battery packs, thought of using a repurposed EV battery pack. I know I would need a huge inverter also. Just curious if anyone has done this or any useful websites about it.
Look up guys will Will Prouse or David Poz on youtube who do videos on it. He has several videos on how to tie salvaged EV batteries into solar inverter setups and they both are frequent posters. I have a few hundred 18650s so I'm thinking of doing something like this myself.
alfadriver said:In reply to mdshaw :
I see a lot of people trying it on University of Tubes videos. But I also think the cost of large storage using LiFePO4 batteries is getting so low, you may be better off getting a large set of those.
I have yet to see that kind of price lowering. I was just pricing out some LiFePO batteries and I was getting $7-10/Ah. For 100Ah, that's $1000 for something the size of a car battery.
I can see using LiFePO for weight savings and energy density, but not for cost savings.
Curtis73 (Forum Supporter) said:alfadriver said:In reply to mdshaw :
I see a lot of people trying it on University of Tubes videos. But I also think the cost of large storage using LiFePO4 batteries is getting so low, you may be better off getting a large set of those.
I have yet to see that kind of price lowering. I was just pricing out some LiFePO batteries and I was getting $7-10/Ah. For 100Ah, that's $1000 for something the size of a car battery.
I can see using LiFePO for weight savings and energy density, but not for cost savings.
I got a Renogy 100ahr battery for $500. And there are quite a few cheap options out there one can use that are in the $500 range if you understand their limitations (mostly they don't have cold temp cut off).
Or if you DIY your own battery- 100ahr 3.2V cells are under $100 right now. I just found some 200ahr cells for $155. A really good BMS is ~100$.
Not as cheap as LiIon, but considering the safety, the current price for DIY solutions is pretty darned good.
The cheapest option for off grid batteries has always been flooded batteries.
It's what I've always used and they work very well
jimbbski said:I've been reading about a company that developing a battery that doesn't use any hard to get or expensive materials. A form of iron or iron oxide is used to store power. Not sure how it works but it's supposed to be way cheaper to make. The last report I read was in the WSJ a few weeks back.
Edison batteries?
Also if DIY is the idea and you want no fire danger, maybe look into saltwater battery's
Antihero (Forum Supporter) said:jimbbski said:I've been reading about a company that developing a battery that doesn't use any hard to get or expensive materials. A form of iron or iron oxide is used to store power. Not sure how it works but it's supposed to be way cheaper to make. The last report I read was in the WSJ a few weeks back.
Edison batteries?
Eh, bad idea. If you can find em their internal resistance is super high- put 3 watts in only 1 watt is stored- but they still use liquid, and it's typically caustic potassium hydroxide last I saw.
In reply to alfadriver :
Where did you find the 200ah for $155? I need 1, for that price I'll get 2. Going to convert our motorhome fridge from propane-a/c to dc.
In reply to mdshaw :
Aliexpress. Although I would go with the DIYsolar group buy for the same cells. They seem to be able to find a reliable source (which is confusing on aliexpress) and get a better deal thanks to really high volumes. A few months ago, I was quoted just under $2000 for 20 270 ahr batteries.
Oh, and these are for 3.2V cells, so you need 4 of them to make a 12V battery for your camper. And a BMS to go with it.
The reason I didn't pull the trigger is that I'm still taking data on how much storage I need to power the entire electrical system- stove, a/c, microwave, coffee machine, dc fridge, heat, hot water, etc. Once we get into the groove of camping, I'll really track the conditions and useage.
Here's a recommended 100ahr battery- https://www.sokbattery.com/products/100ah-12v-lifepo4-deep-cycle-battery
Mind you, given the cycle usage, a flooded lead acid battery would be 200a-hr. That, and when you factor in the number of cycles in the life of the battery, well.
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